My bivy setup will take the place of a tent, but WILL be used in conjunction with a sleeping bag and inflatable sleeping pad (25x72"). There's actually a bit of room for minimal/basic gear in the BA bivy, even once your bag and pad setup are inserted. I'm looking at the packability/weight aspect as well as multi-purpose uses. I figure this whole setup with weigh about 3.5 lbs.; but it should pack better than a tent, be warmer than a tent, and at any point I could eliminate a piece of kit. The BA also vents well, or better than most. Summer hiking/overnighters will be just the bivy and sleeping gear (no tarp), when I wouldn't be carrying much, compared to a hunting setup. Except for the bugs around here, just the tarp could be an option in combination with the bivy footprint.
All that aside, I have a full hammock setup, and a couple of tent setups too... I love the hammock, but hate packing both quilts from a bulk aspect lol.